`H_(3)PO_(2),H_(3)PO_(3)` and `H_(3)PO_(4)` which of them are tribasic acids

Explanation

To determine which of the acids \( H_3PO_2 \), \( H_3PO_3 \), and \( H_3PO_4 \) are tribasic acids, we need to analyze the number of hydroxyl (OH) groups present in each acid. A tribasic acid is defined as an acid that can donate three protons (H⁺ ions), which corresponds to having three hydroxyl groups.

### Step-by-Step Solution:

1. **Identify the Structure of Each Acid**:
- **For \( H_3PO_2 \)**:
- The structure can be represented as \( H_2P(=O)(OH) \).
- It has one hydroxyl group (OH).
- Therefore, it can donate only one proton and is classified as a **monobasic acid**.

2. **Analyze \( H_3PO_3 \)**:
- The structure can be represented as \( HPO(=O)(OH)_2 \).
- It has two hydroxyl groups (OH).
- Therefore, it can donate two protons and is classified as a **dibasic acid**.

3. **Examine \( H_3PO_4 \)**:
- The structure can be represented as \( H_3PO(=O)(OH)_3 \).
- It has three hydroxyl groups (OH).
- Therefore, it can donate three protons and is classified as a **tribasic acid**.

4. **Conclusion**:
- Among the three acids:
- \( H_3PO_2 \) is monobasic.
- \( H_3PO_3 \) is dibasic.
- \( H_3PO_4 \) is tribasic.
- Thus, the only tribasic acid among them is **\( H_3PO_4 \)**.

### Final Answer:
The tribasic acid among \( H_3PO_2 \), \( H_3PO_3 \), and \( H_3PO_4 \) is \( H_3PO_4 \).